Original PIX 506 stopped working after it was placed back into service

We have had a Cisco PIX 506 running for several years and everything was working fine. We decided to replace it for one reason. Sometimes it was if the unit would freeze or hang. We purchased a PIX506E and the configuration of the new PIX506E was identical to the old one, with some exceptions.

Change History for new PIX506E
1. Removed IP addresses that were punched in to allow VNC connections.
2. Removed IPSEC statements for the new 506E (not connecting to another off-site PIX now)

Change History for Original working PIX506
None - everything was left as it always was

Step 1. I removed the original working PIX 506 from the network, and installed the new PIX506E.
Step 2. The new 506E would allow us to access the internet, but we could not access on of our internally hosted SharePoint sites with https assigned. Could navigate to it by server name and port.
Step 3. I removed the new PIX to place on localized hub while browsing through the configuration
Step 4. I re-installed the original perviously working 506 model
Step 5. Once the original was reconnected to the network, we have no internet access at all.
Step 6 I reloaded the original 506, power cycled it, still nothing
Step 7. Our ISP was able to ping our PIX's IP address (static assigned by them)
Step 8. I removed the original PIX and placed the 506E back into service
Step 9. Now this previously working (internet access) 506E would not allow use internet access
Step 10. Removed the 506E and replaced with 506, still no internet access.
Step 11. No access to internet with either PIX now.

What in the world could be going on? NOTHING was changed / modified on the original PIX506, so when it was reconnected to the network, we obviously expected internet access, as well as access to our SharePoint site.

I appreciate your feedback. I am not currently on site with the config info.